1. Field of the Invention
This invention relates in general to switch matrices, and in particular to a switch matrix for satellite payloads with multiple uplink beams and on-board signal processing.
2. Description of Related Art
Communications satellites have become commonplace for use in many types of communications services, e.g., data transfer, voice communications, television spot beam coverage, and other data transfer applications. As such, satellites must provide signals to various geographic locations on the Earth's surface. As such, typical satellites use customized antenna designs to provide signal coverage for a particular country or geographic area.
Many satellite payloads contain analog or digital signal processors. Analog processors are typically used to separate and combine different signals into specific channels (“channelize the signals”), and to switch different parts of the ground-to-satellite (“uplink”) signal to different satellite-to-ground (“downlink”) beams. Digital processors are also used to channelize and switch signals, and may also be used to demodulate, process and remodulate signals. Usually these signal processors are heavy and consume a lot of DC power, so it is advantageous to be as efficient as possible in allocating processing resources to uplink beams.
Typically, the signals (“traffic”) in each uplink beam to the satellite are different, since the population and economy in each uplink region is different. If the amount of traffic in each uplink beam is known before the satellite is launched, and does not vary over the life of the satellite, processing resources can be allocated to uplink beams with fixed connections, which eliminates the need for the switch matrix. Typically, however, the amount of traffic in each uplink beam is either unknown beforehand or varies over time, and thus there must be some sort of switch matrix to reallocate and interconnect uplink beams to the on-board satellite processing resources.
Some traditional switch matrix designs, such as the crossbar switch or the Clos switch matrix, were designed for use in telephone switching networks, and are designed for point-to-point connectivity. Other switch matrices have been designed for connections inside a computer or between networked computers. Some of these designs are not suitable for satellite signals at microwave frequencies, because the related art switch matrix designs suffer from isolation problems at microwave frequencies. Other switch matrices do not provide for point-to-multipoint connectivity without excessive signal losses caused by power splitting. Many designs are also difficult to build out of smaller pieces in a modular manner.
It can be seen, then, that there is a need in the art for a switch matrix that is suitable for use in a spacecraft environment. It can also be seen that there is a need in the art for a switch matrix that provides point-to-multipoint connectivity without excessive signal losses. It can also be seen that there is a need in the art for a switch matrix that provides ease of mechanical design and construction to reduce spacecraft costs.